A single spar aircraft seat frame is described in specification No. GB-A 2022403 and employs a single laterally extending spar secured to the apex of leg subframes and in turn carrying arm-rest frames. Seat pad supports of webbing are resiliently suspended between the arm-rest frames by coil springs and wire hangers. But insofar as the lateral spar is positioned below the arm-rest frames it obstructs the free space of the passenger immediately to the rear. And in the event of a heavy down load, the occupant's legs may come into contact with and be fractured by the laterally extending spar. Moreoever the seat frame is made from metal and is inherently heavier than when carbon fibre reinforced plastics materials and aramid materials are used, e.g. as described in our Patent Specification No. WO-82/03366.